Liquid fuel burner with mixing and igniting means



Mar h 6, 1951 R. s. DAMON Em 2,544,299

LIQUID FUEL BURNER WITH MIXING AND IGNITING MEANS Filed Jan. 2, 1948 PILOT SPACE LIGHT fill w l 1- l cwmz/vr souRc I 1- FLAME BJFFLE CHAMBER INVENTORS RALPH 5. aq/wo/v ROBERTH. HUNTER 'ATTORNE Patented Mar. 6, 1951 mourn rum. nuanmwrrn mxnvd AND rom'rmo MEANS Ralph s. Damon, 'Cleveland,.;and M. ii.

Hunter, Gates Mills, Ohio; said Damon as- -signer to said Hunter Application January 2, 1948, Serial No. 256

6 Claims. (Cl. 158-28) The invention relates to an improved heate system and apparatus of the portable, sparkignited, liquid hydrocarbon burner class.

The apparatus, in the form shown, is for in truck cabs, busses, auto-trailers.,motor boat and other cabins, airplane cockpits and the like; and is applicable to water heaters and boilersparticulariy of the portable type for vehicle and relatively small capacity installations.

A specific object is to .provide a hydrocarbon burner head adapted for electrical spark ignition of injected fuel and with effective provision for protection against overheating of the necessary spark terminal apparatus and against excessive heating of critical parts of the mixer chamber and connected apparatus for atomizing the fuel.

A further object is to provide a hydrocarbon injector, mixer chamber and burner head assembly having several improved features in respect to ignition of the fuel and protection of the injector apparatus against vapor lock and undesirably noisy or inefflcient operation resulting therefrom or connected causes.

In the drawing, Fig. 1 is a diagram showing typical electrical controls and mechanical Jarrangements for attaining the above and other objectives. Fig. 2 is a fragmentary central longitudinal sectional view of the injector and burner head apparatus. Fig. 3 is a detail sectional view thereof as indicated on Fig. 2. Fig. 4 is a frag? mentary view of part of the burner head apparatus as applied to water heater or boiler use. Y

Figs. 1 and 2 show the heat exchange head or portions thereof in typical form, comprising a flame tube I having radiating fins .2 within i'an air-chamber-forming casing 3 having an air ln-.

let duct portion 4 and hot air outlet or discharge duct 4a communicating in suitable fashion (not show) with the space to be heated (or aerated and heated). A power blower is diagrammatically indicated at 5 comprising an electric motor and fan. That and other portions of the apparatus, so far as applicable, may be in accordance with Robert H. Hunter, Patent No. 2,410,881, issuedNovember 12, 1946. I

.A portion of the blower apparatus (usually an impeller separate from that supplying the duct 4) forces atomizlng and/or combustion-complementing air, as through a duct 6, to a fuel and air mixer and injector assembly 1 including a fuel pickup or mixer Venturi tube 8 and fuel jet .9. The burner head includes a burnercone It in sea ed connection with the mixer assembly and with theinlet end of the flame tube 1.

All from the tube 8 is blown through the Venturi'tube l with sufficient force to atomize fuel introduced at the tip of the nozzle, and the atomand to retard the heme velocity and secure an eflicient rate of heat exchange a series of flame baiiles l2 (see Hunter patent) is arranged inside the tube and connected to its wall. The baflies preferably comprise cup-shaped sheet metal elements in stacked self-spacing arrangement and with maze-effecting fingers It in partially overlapped arrangement at the central part of the flame tube (not fully illustrated).

An important feature is that the spark ignition means includes a terminal-supporting and insulating plug ll, essentially of conventional form and purpose, supported by the burner cone III for .thermal protection of its insulation and having its spark terminal so positioned as to assure igniting contact of the spark with fuel at a point such as will normally provide adequate protection against premature ignition and blowback of flame into the burner cone.

The plug ll extends through a wall of the burner cone, being removably secured to said wall by conventional means at 15 (not illustrated in detail, being well known) and the terminal conductor Ii, as shown in Fig. 2, extends through an elongated, i. e. elliptical, opening H in the screen wall H to the sparking point.

In a horizontal installation such as shown by Fig. 2 the spark terminal conductor 16 extends adiacent a fuel-'fllm-supporting ground plate it connected to the flame tube assembly and in position to tend to collect and retain a thin film of fuel thereon exposed to the terminal for ignition by the spark. For effective collection of fuel to form such fllm, the top side of the ground plate I! is dished e. g. cylindrlcally concave on its upper side as suggested by Fig. 3) and its top face is put into communication with such fuel as may condense on the burner cone ill through the lowermost ones I! of the perforations I! in the screen II. The opening I! is made sufficiently large so'that the conductor It, although it may become bent somewhat during insta lation or may be supplied in bent or warped condition. will be closer at its tip to the ground plate 18 than to the periphery of the opening at any point. In

some cases the conductor is purposely bent and the insulation body (porcelain) 2i! of the plug isthen rotated in the receiving opening therefor of the cone l so as to select the most desirable or effective spark gap. The enlarged opening II enables such rotation without likelihood of sparking directly against the screen wall ll. When the desired spark gap is attained, the usual, or a suitable, threaded connector sleeve of the plug assembly is tightened to hold the terminal in place.

The condition or amplitude of the spark and the combustion state can be observed through a sight tube 48 mounted (e. g.) on the burner cone II and generally directed toward the spark gap region.

The outer or smaller end of the burner cone in is threaded at 22 for removable attachment of the atomizer or mixer tube assembly. The mixer tube 8 is removable from the mixer inlet tube So so as to enable selection of different sizes and/or shapes of mixer throats for optimum mating with dif ferent installations; and partly for that reason the discharge endof the tube 8 is flanged at 23 and the flange is clamped between heat barrier (low-heat-conductive) gaskets or washers 24 and 25 inside the threaded attachment sleeve nut 26 which is screwed tightly onto the threads 22 of the burner cone. Theheat barrier connection, in addition to its main purpose viz: prevention of vapor-lock or explosions in the mixer throat due to overheating by conduction, enables the ply connection 32 and a needle valve plug 33. 'The plug 38 extends through a closely embracing sleeve 3B in a counterbore of the fitting 3| to align the plug point with its conventional metering aperture in the fitting. An air-stop seal 35 surrounds the plug stem and occupies a supporting sleeve 36 which is internally threaded to carry the operating stem 31 of the plug. A locking spring 38 around the stem reacts on the sleeve and a needle valve adjusting head-piece 39.

Referring to the controls (Fig. 1), a line 50 connected to the current source incorporates a safety fuse and leads to a blower-motor speedcontrol switch of the double-pole, doublethrow type, the movable element 5la of which is shown in low speed" position.- Closing of the switch 5| in either of its operating positions starts the motor of blower 5; the circuit established thereto in either position flowing through a line 5'! to a variable resistance 51a, thence to the motor and ground 5a thereof. Regardless of the position of the switch element 5l a, closing of it supplies a pilot light 52' to indicate that the heater supply circuit has'been established. Via the line 53 leading to the pilot light a thermostat switch 54, in the space to be heated, controls current supply to a relay 55 and therethrough to another (grounded) thermostat switch 55 in thermo-sensitive relation to the burner head. The thermostat switch 55 is normally closed; opens when the burner starts to function, and then remains open until the burner cools down. Thus, closing ,0! the space thermostat switch energizes the relay 55 thereby closing two normally open switches 58 and 58.

Closing of the switch 58 by-passes the resistance 51a and supplies current to the blower motor at fuel-pick-up speed in relation to the mixer assembly 8, 8 through tube 6, and the motor meanwhile forces air over the flame tube and fin assembly. Concurrently the closing of the relay switch 59, through line 60, starts operation of a fuel pump 6| (or opens a fuel valve if the heater unit has a service supply tank) so that fuel is fed to or maintained in communication with the nozzle or jet 8; and, by energization of a vibrator and coil assembly 62 connected in the circuit at 83 supplies high' voltage intermittent current to the spark plug l4.

When the system is shut down, by op ning of either the space thermostat switch 55 or the heater head thermostat switch 56, the'switches 58 and 59 are opened, cutting off normal operating current to the blower motor and de-energizing the spark coil and fuel pump actuator. Thereupon current still flows through the resistance 51a to supply the blower motor for operation at very low or scavenging speed. Such lowspeed operation is insufficient to cause withdrawal of fuel from the nozzle jet 9, but it is suflicient to sweep any residue of combustible gases out of the burner head and fiame tube, insuring that, upon recycling of the apparatus there will be no explosion. Meanwhile the residual heat in the heat exchange portions of the unit is delivered slowly to the space served. 7

The variation in construction illustrated by Fig. 4 is adapted to water heating or boiler use as previously indicated. Such frequently requires that the flame tube la be placed vertically, being surrounded by awater jacket or reservoir as indicated at 10. In such case the spark terminal may be positioned as at 'H adjacent the defining wall of a central orifice 12 in the screen or partition wall Ila. In that case, a film of fuel is maintained by condensation and drainage around said defining wall to insure ignition, and, due to the concentration or relatively high volume of flow through such relatively large central, orifice, there is little likelihood of blow-back of flame into the burner cone II). In this installation the sight tube 40a is preferably placed in the top wall of the flame tube either vertically or (as shown) directed generally toward the spark point. In both illustrated installations the insulation portions of the spark plug are amply protected against destructive heating, and ignition and proper combustion are effectually assured.

We claim:

1. In a heating apparatus of the type described, means forming a mixing chamber for air and liquid fuel, means to conduct fuel and air to the chamber, means forming a combustion chamber, a metal mix.ure delivery tube of gradually expanding transverse area connecting the two chambers and in sealed'relation thereto adjacent respective chambers, a mixture distributor plate across the larger end of the tube and having a multiplicity of openings therethrough including one relatively large opening, electrical ground surface means adjacent said larger opening adapted and arranged to retain a film of condensed liquid fuel thereon, and a spark plug incent said larger opening and in sparking relation with said ground surface means, said larger opening providing clearance for the spark terminal.

2. In a heater apparatus of the liquid-hydrocarbon-burner, electrical-spark-ignition type, a mixer device and means to conduct fuel and air thereto, a burner head and associated means forming a combustion chamber, said head including a conical metal tube connecting the mixer device and chamber and with its large end in sealed relation to the chamber, a spark plug insulatingly carried by the tube, an apertured distributor plate between the tube and combustion chamber, a fuel-film-collector plate inside the burner chamber and electrically grounded to the plate and tube, said spark plug having a spark terminal projecting through one of the apertures of the distributor plate and into sparking relation with the film collector plate.

3. In an air operated spark ignited, liquidfuel-burner, means forming a mixing chamber and a combustion chamber spaced apart horizontally, means to conduct fuel and air to the mixing chamber, a conical metal tube extending between the two chambers, sealingly connected at its small end with the mixing chamber and at its large end with the combustion chamber, an apertured metal screen plate bridging said large end, an electrically grounded flash pan inside the combustion chamber and positioned with an upwardl exposed fuel-film-supporting surface in receiving relation to liquid fuel that may drain through apertures of the plate from the Lube wall, and an electrical spark plug insulatingly carried by the tube wall and projecting through an aperture of the plate, out of contact therewith, into sparking relation to said surface of the flash pan.

4. The apparatus according to claim 3, wherein the lowermost inclined surface of the tube wall is contiguous to an adjacent margin of the flash pan and at least one of the apertures of the screen plate is adjacent said lowermost surface so as to afford direct fuel communication from the tube to the flash pan.

5. In a burner apparatus of the class described; a metal mixer device having a through orifice to receive air and having an injector nozzle opening into the orifice, means to conduct air and fuel to said orifice and nozzle, means forming a combustion chamber, a metal distributor tube for conveying atomized fuel from the orifice to the chamber, means to ignite the atomized fuel for propagation of flame thereof in the combustion chamber, and a sealing connection between the tube and the mixer device comprising a flange on one of said metal elements, a sleeve nut on the other, and a pair of non-metallic heat barrier washers on opposite sides of the flange and arranged to be compressed thereagainst by tightening of the sleeve nut.

6. In a burner apparatus of the class described, a tubular metal mixer device adapted to have air passed therethrough, an injector nozzle opening into the path of such air, means forming a combustion chamber at the outlet end of the mixer device, a tubular metal distributor device for conveying atomized fuel to the chamber, means to ignite the fuel and air mixture in the combustion chamber, the distributor device being metallically connected to the chamber forming means, a clamping collar adjustably connected with one of said devices and having an annular shoulder around the other device, and non-metallic heat barrier washers one of which lies between the two devices and the other of which lies between said annular shoulder and said other device for establishment of a low-heat-conductive seal between said devices by adjustment of the clamping collar.

RALPH S. DAMON. ROBERT H. HUNTER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,625,629 Scott Apr. 19, 1927 1,676,501 Moors July 10, 1928 1,924,938 Lewis Aug. 29, 1933 2,230,446 Baker Feb. 4, 1941 2,410,881 Hunter Nov. 12, 1946 

